Tuesday, March 31, 2015, 5:10 p.m.

Longer tamoxifen use cuts breast-cancer deaths, study finds

Women with the most common type of breast cancer live longer and are less likely to have their tumors return if they are given tamoxifen for a decade rather than the currently recommended five years, a study found.

The research presented Wednesday at the San Antonio Breast Cancer Symposium suggest women who are on tamoxifen and those who recently completed five years of therapy should continue taking the drug for another five years, said Richard Gray, a professor of medical statistics at the University of Oxford in England.

The findings should change the standard of care for women whose tumors are fueled by the hormone estrogen, Gray said in a telephone interview. Patients have been told to take tamoxifen for five years after their initial diagnosis and treatment because it slashes their risk by one-third. Now they can do even better, cutting the risk in half, he said.

“Breast cancer is a disease with a very long natural history, and there is a chance of recurrence even after 10 years,” said Gray, one of the study researchers. “We know now that definitively women should continue tamoxifen for 10 years. The benefits were much larger than the risks.”

Additional studies are under way using the newer drugs, such as Pfizer Inc.’s Aromasin, AstraZeneca PLC’s Armidex and Novartis AG’s Femara. It’s not clear yet whether longer use of those drugs will also yield greater benefits, Gray said.

About 1 in 8 women will develop breast cancer in her lifetime, making it the most common tumor in women. Almost 230,000 women were diagnosed with the disease in 2012, and more than 39,900 died from it, according to the American Cancer Society.